You create a Microsoft ASP.NET application by using the Microsoft .NET Framework version 3.5. You create a Web form by using ASP.NET AJAX. 
You write the following client-script code fragment to handle the exceptions thrown from asynchronous postbacks：  
01 <script type="text/javascript">  
02   function pageLoad（）  
03   {  
04     var pageMgr = 
05       Sys.WebForms.PageRequestManager.getInstance（）；  
06 ► 
07   }  
08  
09   function errorHandler（sender， args）  
10   {  
11 ► 
12   }  
13 </script>
You need to ensure that the application performs the following tasks： 
use a common client-script function named errorHandler. 
udpdate a Label control that has an ID named lblError with the error message. 
prevent the browser from displaying any message box or Javascript error.  
What should you do？（）

You create a Microsoft ASP.NET application by using the Microsoft .NET Framework version 3.5. You write the following code segment to create a client-script function：  
01 function updateLabelControl（labelId， newText） { 
02 ► var label = $find（labelId）； 
03 ► label.innerHTML = newText；  
04 }  
The client script function uses ASP.NET AJAX and updates the text of any Label control in the Web form. 
When you test the client script function， you discover that the Label controls are not updated. You receive the following JavaScript error message in the browser： "’null’ is null or not an object." You need to resolve the error.
What should you do？（）